The invention relates to a machine frame with a movable scaffold for the tool area of an injection molding machine. The scaffold is arranged between a stationary tool clamping plate and a tool clamping plate that is displaceable on a slide carriage, for receiving two halves, respectively, of a forming tool. The movable tool clamping plate is displaceable on a guideway of the machine frame. The tool clamping plates are connected by columns extending into both tool clamping plates or, advantageously, supported in a cantilever fashion on the movable tool clamping plate. The columns are adjusted to an appropriate tool height by means of a tool height adjusting device.
For injection molding machines having large tool clamping plates, a large and stable machine frame for supporting the tool clamping plates is necessary. The machine frame is formed of longitudinal bars kept at a predetermined distance by cross-struts. On the upper surface of the machine frame, guideways for the slide carriage of the movable tool clamping plate are located. If required, a movable cross-strut with rollers for automatic tool exchange, according to DE-OS 4,039,325 is displaceable on the guideways. The drawback of this construction is that the rigidity required by the large machine frame, with the thereon displaceable tool clamping plate, necessitates a correspondingly high building structure for mounting the machine.
To lower the center of gravity, it is proposed in DDR patent 130,118, to form the tool clamping plates as isosceles triangles which are aligned with their apexes vertically downward between the guideways of the machine frame. However, the drawback of this solution is that the tool clamping surfaces are reduced and the force distribution and dimensioning are uneven, because mainly square and rectangular forming tools are used and the corresponding tool clamping plates are normalized accordingly. This also raises a further problem of shaping and forming the scaffold displaceable in the tool area of the injection molding machine which should be positioned very deeply downward. The movable scaffold that enters the tool area to enable maintenance, repair or for removal purposes, should simultaneously fulfill a safety function that provides for automatic switch-off of the machine in case a foreign element penetrates the tool area.
A corresponding solution is disclosed in DDR Patent 154,121. According to this solution, the scaffold occupies the total tool area and is supported on a connecting spring-biased mechanism and actuates an electrical switching mechanism after corresponding displacement. This solution is very costly and requires a vertical displacement space which is not available with integration of an automatic tool exchange system.